MAVEN Observes Mars Moon Phobos in the Mid- and Far-Ultraviolet
February 29, 2016

NASA scientists are closer to solving the mystery of how Mars' moon Phobos
formed.

In late November and early December 2015, NASA's Mars Atmosphere and Volatile
Evolution (MAVEN) mission made a series of close approaches to the Martian
moon Phobos, collecting data from within 300 miles (500 kilometers) of
the moon.

[Graphic]
The orbit of MAVEN sometimes crosses the orbit of Phobos. This image shows
the configuration of the two orbits in early December 2015, when MAVEN's
Phobos observations were made.
Credits: CU/LASP and NASA

Among the data returned were spectral images of Phobos in the ultraviolet.
The images will allow MAVEN scientists to better assess the composition
of this enigmatic object, whose origin is unknown.

[Image]
Phobos as observed by MAVEN's Imaging Ultraviolet Spectrograph. Orange
shows mid-ultraviolet (MUV) sunlight reflected from the surface of Phobos,
exposing the moon's irregular shape and many craters. Blue shows far ultraviolet
light detected at 121.6 nm, which is scattered off of hydrogen gas in
the extended upper atmosphere of Mars. Phobos, observed here at a range
of 300km, blocks this light, eclipsing the ultraviolet sky.
Credits: CU/LASP and NASA

Comparing MAVEN's images and spectra of the surface of Phobos to similar
data from asteroids and meteorites will help planetary scientists understand
the moon's origin - whether it is a captured asteroid or was formed in
orbit around Mars. The MAVEN data, when fully analyzed, will also help
scientists look for organic molecules on the surface. Evidence for such
molecules has been reported by previous measurements from the ultraviolet
spectrograph on the Mars Express spacecraft.

The observations were made by the Imaging Ultraviolet Spectrograph instrument
aboard MAVEN.

MAVEN's principal investigator is based at the University of Colorado's
Laboratory for Atmospheric and Space Physics, and NASA's Goddard Space
Flight Center in Greenbelt, Maryland, manages the MAVEN project. Partner
institutions include Lockheed Martin, the University of California at
Berkeley, and NASA's Jet Propulsion Laboratory.